MGA Forum

The manual calls for Castrol Hypoy 90w gear oil in the rear axle, which is no longer available. I do have 2 quarts of Castrol Hypoy C 80w-90 gear oil. Does anyone know if the Hypoy C is the same as the original Hypoy and should I use it?

Thanks

Andy

I can't find any specs on Castrol Hypoy gear oil, but assume that it's a GL4 oil. Hypoy C is a GL5 gear oil that may affect yellow metals such as copper, bronze and brass. So to be safe I'll just refill the rear axle with Stay Lube GL4 85W90 gear oil.

Andy

Andy I used the GL5 80 90 blend,




I just saw the article on your build in a sportscar magazine that my brother gave me, very nice.

Hi Andy,
Your Coupe` is exactly like our car. Audi Red.
Be sure to use Hypoid Gear oil your Diffenential, to prevent premature gear failure.
This lubricant is designed to with stand the much greater slide pressure crerated between Hypoid machined gears.
The straight oil suited the old bevel gears [ as fitted to early "T" Types ] is best not used in your hypoid diff..
Duiring our car`s re-built, my diff. was altered to 3.9/1 gears--it goes beautifully with a 5 speed Toyota gearbox making the Coupe` a great touring car.
These gears were second hand, previously used in another car. The contact area on the teeth were lightly marked.
A transmission shop lapped the gears, in an effort to fix a potential "Hum in the Bum' caused by the tooth contact meshing.
At the usual 35mph, it had a slight "Hum" , that disappointed me.
So I drained the EP 90 grade oil---Re-Filled with EP 140 grade oil--added a tube gear additive [ not sure if a brand name can be used here ] and
the diff. is now quiet after 20,000 miles of running.
These gear additives work well. TC Gearboxes get to run quite warm, at the end of a days motoring.
Add a tube of this white magic and the gears become quieter and it runs cooler.
EP oils must be about in the U S .
What does Cecelia at S.F. say about stocks?
Good motoring.
Ian Cowen.
Gold Coast Australia.

Thanks for your replies guys. Bob, I was very happy when Vintage Motorsports asked to write an article about my car. It was a complete basket case before. Ian the oil I have bought is hypoid gear oil which I have used before but I have some hypoy C lying around the garage and that's where it will stay.

The only reason I'm changing the oil again is an annoying drip from the drain plug in the diff housing which I've tried to seal many times with Teflon tape. This time I cleaned the threads with a 1/2" x 14 tap and die and have used thread sealant on the plug. I hope this works.

Thanks

Andy
MG (Audi "Brilliant Red" Coupe